Although wastewater treatment facilities are effective in the removal of solid wastes and bacterial contaminants, a variety of harmful chemical pollutants are able to pass into drinking water. In Kentucky, pesticides from farm runoff and pharmaceutical waste from hospitals frequently enter wastewater. Catastrophic events like the 2014 Elk River spill meant toxic 4-methylcyclohexanemethanol was detected in the Ohio river, even where the city of Louisville derives a majority of its drinking water. Our lab develops materials and analytical techniques (Raman Spectroscopy) for improving a technology called photocatalytic degradation, which uses special materials (photocatalysts) that harvest sunlight to break down chemical pollutants. For example, we can embed the photocatalyst into a buoyant supporting material such as polydimethylsiloxane (PDMS), an environmentally inert polymer that we can produce as buoyant beads embedded with TiO2 as a photocatalyst. We demonstrate this material on a model pollutant to suggest ways to improve the process further. We have also developed Raman spectroscopy techniques for monitoring reactions in real time, 100 times quicker than conventional methods of analysis, with some disadvantages: Raman is not a very sensitive technique, and it is unreliable for accurately tracking the change in the concentration of pollutants over time. Here, gold nanoparticles were used to enhance sensitivity and accuracy and thus study a broader range of pollutants. The use of nanoparticles presents an additional issue because nanoparticles tend to aggregate together when subjected to conditions necessary to monitor reactions, and thus signal diminishes as a function of time. This was addressed by introducing a secondary capping agent which stabilized growing nanoparticle clusters and prevented them from aggregating to the point of signal loss. Overall, this work serves to broaden the selection of pollutants that can be studied using Raman spectroscopy, and adds to our tools for ensuring the water security for Kentucky.

Although wastewater treatment facilities are effective in the removal of solid wastes and bacterial contaminants, a variety of harmful chemical pollutants are able to pass into drinking water. In Kentucky, pesticides from farm runoff and pharmaceutical waste from hospitals frequently enter wastewater. Catastrophic events like the 2014 Elk River spill meant toxic 4-methylcyclohexanemethanol was detected in the Ohio river, even where the city of Louisville derives a majority of its drinking water. Our lab develops materials and analytical techniques (Raman Spectroscopy) for improving a technology called photocatalytic degradation, which uses special materials (photocatalysts) that harvest sunlight to break down chemical pollutants. For example, we can embed the photocatalyst into a buoyant supporting material such as polydimethylsiloxane (PDMS), an environmentally inert polymer that we can produce as buoyant beads embedded with TiO2 as a photocatalyst. We demonstrate this material on a model pollutant to suggest ways to improve the process further. We have also developed Raman spectroscopy techniques for monitoring reactions in real time, 100 times quicker than conventional methods of analysis, with some disadvantages: Raman is not a very sensitive technique, and it is unreliable for accurately tracking the change in the concentration of pollutants over time. Here, gold nanoparticles were used to enhance sensitivity and accuracy and thus study a broader range of pollutants. The use of nanoparticles presents an additional issue because nanoparticles tend to aggregate together when subjected to conditions necessary to monitor reactions, and thus signal diminishes as a function of time. This was addressed by introducing a secondary capping agent which stabilized growing nanoparticle clusters and prevented them from aggregating to the point of signal loss. Overall, this work serves to broaden the selection of pollutants that can be studied using Raman spectroscopy, and adds to our tools for ensuring the water security for Kentucky.